It is assumed that basic concepts of OPC UA information modelling, OPC Unified Architecture - Part 100, and OPC UA for Machinery - Part 1 are understood in this specification. This specification will use these concepts to describe the OPC UA for Compressed Air Systems Information Model. For the purposes of this document, the terms and definitions given in OPC 10000-1, OPC 10000-3, OPC 10000-4, OPC 10000-5, OPC 10000-7, OPC 10000-100, OPC 40001-1, as well as the following apply.

Note that OPC UA terms and terms defined in this specification are italicizedin the specification.

Piping and all Componentsbetween at least two distinct points, the inputs and outputs of the Airnet, in a Compressed Air System.

Note 1 to entry: A Componentcan be connected to multiple Airnets.

Note 2 to entry: Airnetsmay touch or overlap each other.

Note 3 to entry: For examples on how Airnetscan be used in the context of this specification see chapter 6.

Identifiable and browsable element in a Compressed Air System.

Note 1 to entry: CASPartsdefined in this specification are: Airnet, all Components,Main Control System.

CASPartthat serves a particular purpose in compressed air generation, treatment, measurement, or storage.

Note 1 to entry: Components defined in this specification are: Charging System, Compressor, Condensate Drain, Condensate Separator, Converter, Cooling System, Dryer, Filter, Heat Recovery System, Receiver, Sensor.

Note 2 to entry: A Component may be connected to no, one, or more than one Airnet.

System that generates compressed air, consists of Componentsand at least one Airnet, and is commonly equipped with one Main Control System.

Specific type of a Componentand value of the ComponentClass Variableof an instance of the FunctionalGroupDesign of a Component.

EXAMPLE 1The compressor C1 is of the ComponentClassAxial turbo compressor.

EXAMPLE 2The filter F1 is of the ComponentClassActivated carbon filter.

Connection point of a Compressed Air System to subsequent machines or systems.

Note 1 to entry: Usually the Customer Distribution Point is located at one of the outlets of an Airnet.

Note 2 to entry: The Customer Distribution Pointprovides Variables and/or Objects which describe the conditions of the compressed air.

Specific class of a CASPartand value of the DeviceClass Propertyof an instance of the FunctionalGroupIdentification of a CASPart.

Note 1 to entry: Available DeviceClassesfor CASPartof this specification are listed in Table 9.

EXAMPLE 1The compressor C1 is of the DeviceClassCompressor.

EXAMPLE 2The filter F1 is of the DeviceClassFilter.

Instance of the FunctionalGroupType or one of its subtypes.

Note 1 to entry: In this specification, FunctionalGroupusually refers to an instance of a Compressed Air System specific ObjectTypelike OperationalType, AnalysesType, or DesignType.

EXAMPLE 1The compressor C1 has the FunctionalGroups Identification, Design, and Operational.

BrowseNameof instances of the OptionalPlaceholder Object <ComponentsGroup> of instances of the ObjectTypeComponentsGroupType.

Note 1 to entry: Available GroupNamesfor part groups of this specification are listed in Table 9.

EXAMPLE 1The Object for organizing all compressors in this Compressed Air Systemuses the GroupName Compressors.

EXAMPLE 2The Object for organizing all Airnetsin this Compressed Air Systemuses the GroupName Airnets.

A Componentis Integrated if the Main Control Systemhas control over the generation or treatment of compressed air.

Note 1 to entry: A compressor is Integrated if the Main Control Systemhas control over the loaded state.

Note 2 to entry: The Main Control Systemcan switch a Componentbetween the two states Integratedand Isolated.

A Componentis Isolatedif the Main Control Systemhas no control over the generation or treatment of compressed air.

Note 1 to entry: A Component is Isolatedif the Main Control Systemdoes not control the loaded state.

Note 2 to entry: The Main Control Systemcan switch a Componentbetween the two states Integratedand Isolated.

CASPartthat controls all Componentsand Airnetssimultaneously, represents the Compressed Air System, and serves for communication between the Componentsand higher-level systems.

The actual main function of Componentsis not specified in this specification. The following examples of Main Functionsdo not imply the actual function of the referenced Component.

EXAMPLE 1Charging system: to keep pressure upstream above a set minimum pressure or within a set pressure range

EXAMPLE 2Compressor: to deliver compressed air into the piping with an expected volume flow and at an expected pressure

EXAMPLE 3Condensate drain: to remove condensate from the compressed air piping or a condensate storage to outside the pressure system

EXAMPLE 4Condensate separator: to separate the hydrocarbon contents from the condensate to create a clean condensate that can easily be disposed of

EXAMPLE 5Converter: to eliminates hydrocarbons from the compressed air stream to create class 1 (and better) oil free air

EXAMPLE 6Cooling system: to reduce the compressed air temperature to a desired level

EXAMPLE 7Dryer: to remove moisture from compressed air and dry compressed air to a pressure dew point below the required value

EXAMPLE 8Filter: to remove particles and aerosols from the compressed air flow

EXAMPLE 9Heat recovery system: Main function: to heat up a material or substance flow by using the heat generated by the compressed air system

EXAMPLE 10Receiver: to store compressed air and provide a buffer

EXAMPLE 11Sensor: to measure specific parameters in the compressed air system and provide the data

A Variablerepresenting physical measurements performed by a sensor, or calculations performed by a CASPartor the Main Control Systemto simulate a physical measurement.

Note 1 to entry: A physical quantity may be measured by an external sensor but is assigned to a specific CASPart.

Note 2 to entry: The measuring sensor may be integrated into the CASPart.

Note 3 to entry: A calculation performed on the Main Control Systemwhich is used by a Componentshall be assigned to that Component.

EXAMPLE 1A temperature Quantityis measured by an internal sensor of a compressor at its outlet.

EXAMPLE 2A pressure Quantityis measured by an external sensor at the inlet and outlet of a filter.

EXAMPLE 3The isentropic efficiency of a compressor is a Quantitywhich is calculated by the Main Control Systembut assigned to the compressor.

The actual requirements of anAirnetare not specified in this specification. The following examples of Requirementsdo not imply the actual requirements of an Airnet.

EXAMPLE 1The Airnet pressure shall be within range.

EXAMPLE 2The dew point shall be within range.

EXAMPLE 3The volume flow rate shall be within range.

A compressor is Unavailableif it cannot be Integratedand controlled by the Main Control System.

Note 1 to entry: The Main Control Systemcannot switch a compressor from Unavailableto any other state.

EXAMPLE 1A compressor in an error state may be Unavailable.

CASCompressed Air System

HOCHeat of Compression Dryer

KPIkey performance indicator

MCSMain Control System

VSDVariable Speed Drive

Nodedefinitions are specified using tables (see Table 2 ).

Attributesare defined by providing the Attributename and a value, or a description of the value.

Referencesare defined by providing the ReferenceTypename, the BrowseNameof the TargetNodeand its NodeClass.

• If the TargetNodeis a component of the Nodebeing defined in the table the Attributesof the composed Nodeare defined in the same row of the table.
• The DataTypeis only specified for Variables; “[<number>]” indicates a single-dimensional array, for multi-dimensional arrays the expression is repeated for each dimension (e.g. [2][3] for a two-dimensional array). For all arrays the ArrayDimensionsis set as identified by <number> values. If no <number> is set, the corresponding dimension is set to 0, indicating an unknown size. If no number is provided at all the ArrayDimensionscan be omitted. If no brackets are provided, it identifies a scalar DataTypeand the ValueRankis set to the corresponding value (see OPC 10000-3). In addition, ArrayDimensionsis set to null or is omitted. If it can be Any or ScalarOrOneDimension, the value is put into “{<value>}”, so either “{Any}” or “{ScalarOrOneDimension}” and the ValueRankis set to the corresponding value (see OPC 10000-3) and the ArrayDimensionsis set to null or is omitted. Examples are given in Table 1 .

Table 1– Examples of DataTypes

Notation	DataType	ValueRank	ArrayDimensions	Description
0:Int32	0:Int32	-1	omitted or null	A scalar Int32.
0:Int32[]	0:Int32	1	omitted or {0}	Single-dimensional array of Int32 with an unknown size.
0:Int32[][]	0:Int32	2	omitted or {0,0}	Two-dimensional array of Int32 with unknown sizes for both dimensions.
0:Int32[3][]	0:Int32	2	{3,0}	Two-dimensional array of Int32 with a size of 3 for the first dimension and an unknown size for the second dimension.
0:Int32[5][3]	0:Int32	2	{5,3}	Two-dimensional array of Int32 with a size of 5 for the first dimension and a size of 3 for the second dimension.
0:Int32{Any}	0:Int32	-2	omitted or null	An Int32 where it is unknown if it is scalar or array with any number of dimensions.
0:Int32{ScalarOrOneDimension}	0:Int32	-3	omitted or null	An Int32 where it is either a single-dimensional array or a scalar.

• The TypeDefinition is specified for Objectsand Variables.
• The TypeDefinition column specifies a symbolic name for a NodeId, i.e. the specified Nodepoints with a HasTypeDefinition Referenceto the corresponding Node.
• The ModellingRuleof the referenced component is provided by specifying the symbolic name of the rule in the ModellingRulecolumn. In the AddressSpace, the Nodeshall use a HasModellingRule Referenceto point to the corresponding ModellingRule Object.

If the NodeIdof a DataTypeis provided, the symbolic name of the Noderepresenting the DataTypeshall be used.

Note that if a symbolic name of a different namespace is used, it is prefixed by the NamespaceIndex(see 3.4.2.2).

Nodesof all other NodeClassescannot be defined in the same table; therefore only the used ReferenceType, their NodeClassand their BrowseNameare specified. A reference to another part of this document points to their definition.

Table 2illustrates the table. If no components are provided, the DataType, TypeDefinition and ModellingRule columns may be omitted and only a Comment column is introduced to point to the Nodedefinition.

Table 2– Type Definition Table

Attribute	Value
Attribute name	Attribute value. If it is an optional Attribute that is not set “--“ will be used.
References	NodeClass	BrowseName	DataType	TypeDefinition	Other
ReferenceType name	NodeClassof the TargetNode.	BrowseNameof the target Node. If the Referenceis to be instantiated by the server, then the value of the target Node’s BrowseName is “--“.	DataType of the referenced Node, only applicable for Variables.	TypeDefinitionof the referenced Node, only applicable for Variablesand Objects.	Additional characteristics of the TargetNodesuch as the ModellingRuleor AccessLevel.
NOTE Notes referencing footnotes of the table content.

Components of Nodescan be complex that is containing components by themselves. The TypeDefinition, NodeClassand DataType can be derived from the type definitions, and the symbolic name can be created as defined in 3.4.3.1. Therefore, those containing components are not explicitly specified; they are implicitly specified by the type definitions.

The Other column defines additional characteristics of the Node. Examples of characteristics that can appear in this column are show in Table 3.

Table 3– Examples of Other Characteristics

Name	Short Name	Description
0:Mandatory	M	The Node has the Mandatory ModellingRule.
0:Optional	O	The Node has the Optional ModellingRule.
0:MandatoryPlaceholder	MP	The Node has the MandatoryPlaceholder ModellingRule.
0:OptionalPlaceholder	OP	The Node has the OptionalPlaceholder ModellingRule.
ReadOnly	RO	The Node AccessLevelhas the CurrentReadbit set but not the CurrentWritebit.
ReadWrite	RW	The Node AccessLevel has the CurrentRead and CurrentWrite bits set.
WriteOnly	WO	The Node AccessLevel has the CurrentWritebit set but not the CurrentReadbit.

If multiple characteristics are defined they are separated by commas. The name or the short name may be used.

The NodeIdsof all Nodesdescribed in this standard are only symbolic names. Annex Adefines the actual NodeIds.

The symbolic name of each Nodedefined in this document is its BrowseName, or, when it is part of another Node, the BrowseNameof the other Node, a “.”, and the BrowseNameof itself. In this case “part of” means that the whole has a HasPropertyor HasComponent Referenceto its part. Since all Nodesnot being part of another Nodehave a unique name in this document, the symbolic name is unique.

The NamespaceUrifor all NodeIdsdefined in this document is defined in Annex A. The NamespaceIndexfor this NamespaceUriis vendor-specific and depends on the position of the NamespaceUriin the server namespace table.

Note that this document not only defines concrete Nodes, but also requires that some Nodesshall be generated, for example one for each Sessionrunning on the Server. The NodeIdsof those Nodesare Server-specific, including the namespace. But the NamespaceIndexof those Nodescannot be the NamespaceIndexused for the Nodesdefined in this document, because they are not defined by this document but generated by the Server.

The text part of the BrowseNamesfor all Nodesdefined in this document is specified in the tables defining the Nodes. The NamespaceUrifor all BrowseNamesdefined in this document is defined in Annex A.

If the BrowseNameis not defined by this document, a namespace index prefix like ‘0:EngineeringUnits’ or ‘2:DeviceRevision’ is added to the BrowseName. This is typically necessary if a Propertyof another specification is overwritten or used in the OPC UA types defined in this document. Table 184provides a list of namespaces and their indexes as used in this document.

The Attributesof Nodes, their DataTypesand descriptions are defined in OPC 10000-3. Attributes not marked as optional are mandatory and shall be provided by a Server. The following tables define if the Attributevalue is defined by this specification or if it is server-specific.

For all Nodesspecified in this specification, the Attributesnamed in Table 4shall be set as specified in the table.

Table 4– Common Node Attributes

Attribute	Value
DisplayName	The DisplayNameis a LocalizedText. Each server shall provide the DisplayNameidentical to the BrowseNameof the Nodefor the LocaleId “en”. Whether the server provides translated names for other LocaleIds is server-specific.
Description	Optionally a server-specific description is provided.
NodeClass	Shall reflect the NodeClassof the Node.
NodeId	The NodeIdis described by BrowseNamesas defined in 3.4.2.1.
WriteMask	Optionally the WriteMask Attributecan be provided. If the WriteMask Attributeis provided, it shall set all non-server-specific Attributesto not writable. For example, the Description Attributemay be set to writable since a Servermay provide a server-specific description for the Node. The NodeIdshall not be writable, because it is defined for each Nodein this specification.
UserWriteMask	Optionally the UserWriteMask Attributecan be provided. The same rules as for the WriteMask Attributeapply.
RolePermissions	Optionally server-specific role permissions can be provided.
UserRolePermissions	Optionally the role permissions of the current Session can be provided. The value is server-specific and depend on the RolePermissions Attribute(if provided) and the current Session.
AccessRestrictions	Optionally server-specific access restrictions can be provided.

For all Objectsspecified in this specification, the Attributesnamed in Table 5shall be set as specified in the table. The definitions for the Attributescan be found in OPC 10000-3.

Table 5– Common Object Attributes

Attribute	Value
EventNotifier	Whether the Nodecan be used to subscribe to Eventsor not is server-specific.

For all Variablesspecified in this specification, the Attributesnamed in Table 6shall be set as specified in the table. The definitions for the Attributescan be found in OPC 10000-3.

Table 6– Common Variable Attributes

Attribute	Value
MinimumSamplingInterval	Optionally, a server-specific minimum sampling interval is provided.
AccessLevel	The access level for Variablesused for type definitions is server-specific, for all other Variablesdefined in this specification, the access level shall allow reading; other settings are server-specific.
UserAccessLevel	The value for the UserAccessLevel Attributeis server-specific. It is assumed that all Variablescan be accessed by at least one user.
Value	For Variablesused as InstanceDeclarations,the value is server-specific; otherwise it shall represent the value described in the text.
ArrayDimensions	If the ValueRankdoes not identify an array of a specific dimension (i.e. ValueRank<= 0) the ArrayDimensionscan either be set to null or the Attributeis missing. This behavior is server-specific. If the ValueRankspecifies an array of a specific dimension (i.e. ValueRank> 0) then the ArrayDimensions Attributeshall be specified in the table defining the Variable.
Historizing	The value for the Historizing Attributeis server-specific.
AccessLevelEx	If the AccessLevelEx Attributeis provided, it shall have the bits 8, 9, and 10 set to 0, meaning that read and write operations on an individual Variableare atomic, and arrays can be partly written.

For all VariableTypesspecified in this specification, the Attributesnamed in Table 7shall be set as specified in the table. The definitions for the Attributescan be found in OPC 10000-3.

Table 7– Common VariableType Attributes

Attributes	Value
Value	Optionally a server-specific default value can be provided.
ArrayDimensions	If the ValueRankdoes not identify an array of a specific dimension (i.e. ValueRank<= 0) the ArrayDimensionscan either be set to null or the Attributeis missing. This behavior is server-specific. If the ValueRankspecifies an array of a specific dimension (i.e. ValueRank> 0) then the ArrayDimensions Attributeshall be specified in the table defining the VariableType.

For all Methodsspecified in this specification, the Attributesnamed in Table 8shall be set as specified in the table. The definitions for the Attributescan be found in OPC 10000-3.

Table 8– Common Method Attributes

Attributes	Value
Executable	All Methodsdefined in this specification shall be executable (Executable Attributeset to “True”), unless it is defined differently in the Methoddefinition.
UserExecutable	The value of the UserExecutable Attributeis server-specific. It is assumed that all Methodscan be executed by at least one user.